1. Field of the Invention
The present invention relates to an endoscope provided with a switch valve for enabling air, gas and water to be selectively supplied.
2. Description of the related art including information disclosed under .sctn..sctn.1.97-1.99
Generally, there is the possibility that inflammable gas remains in the cavity, particularly in the lower digestive organs such as the intestines of a human body. When the high frequency treatment is applied, using the endoscope, to the cavity of the human body in which this inflammable gas remains, therefore, there is the danger that the inflammable gas is burst up by high frequency energy caused by the treatment. In order to prevent this, noninflammable gas such as carbon dioxide is supplied into the cavity through the endoscope to replace the inflammable gas before the high frequency treatment is applied.
Endoscopes which have a unit for supplying a noninflammable gas into a body cavity, as well as an air/water supply unit, is disclosed in Japanese Utility Model Disclosures No. 60-32902 and No. 61-29704. The gas-supplying unit comprises a gas supply pipe and a gas control valve. The endoscope has an air/water supply button and a gas supply button. The air/water supply button is depressed to supply either air or water through an air/water supply pipe into a body cavity. The gas supply button is depressed to supply the non-inflammable gas into a body cavity. These buttons are arranged side by side. Provided with two supply units, the endoscope is relatively large. Further, since the endoscope has two buttons which must be selected and depressed, the operation efficiency of the endoscope is rather low.
In most cases, once the air/water supply unit or the gas supply unit has been operated, thus supplying air or water, or alternatively a non-inflammable gas, into a body cavity, the other supply unit need not be operated. In view this fact, it would suffice to use only one supply unit to supply air or water, or the non-inflammable gas into a body cavity.
Japanese Utility Model Disclosure No. 57-103621, discloses an endoscope wherein two kinds of valve assemblies, one for switching air and water and the other for switching gas and water, can be incorporated into a valve seat at the operating section thereof. The endoscope of this type can be small-sized and its operation is easy because it has no independent gas supply line.
In the case of the gas and water switching valve assembly, however, the gas passage is sealed at the upper and lower sides thereof by seal rings which are made of resilient material and which are pressed against the metal wall of the passage due to their resiliency. Their sealing capacity is thus limited. Further, there is the danger that gas pressurized so high as to overcome their sealing capacity may be supplied because the gas bomb in which the highly-pressurized gas is contained and which is connected directly to the endoscope is used as the gas source. This is caused in a case where the user makes a mistake in adjusting the supply pressure of gas at the outlet of the gas bomb because the endoscope is not provided with a relief valve. When the gas pressurized so high as to overcome the sealing capacity of the seal rings is supplied into the cavity of a patient, he will be damaged heavily. Furthermore, there is also the danger that gas not high in pressure but unnecessarily large in amount may be supplied to the patient when the seal members exchanged in the valve assembly have already something of flaws.